$1.50 for an adult mouse from the local reptile specialty shop, a bit less for younger/smaller mice, and more for rats based on their size as well. I've found that the cheapest option is to buy bulk frozen from somewhere like themousefactory.com, even after you factor in shipping costs. The most expensive option based on my personal situation is buying live/frozen from "big box" pet stores like PETsMART and PetCo.